) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins

The effect of arsenate (As 5+ ) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins (PCs) were investigated. C. vulgaris was tolerant to As 5+ at up to 200 mg/L and was capable of consistently removing around 70% of the As 5+ present in growth media over a wide range of exposure concentrations. Spectral analysis revealed that PCs and their arsenic-combined complexes were absent indicating that the high bioaccumulation and tolerance to arsenic observed was not due to intracellular chelation. In contrast, GSH was found in all samples ranging from 0.8 mg/L in the control to 6.5mg/L in media containing 200 mg/L As 5+ suggesting that GSH plays a more prominent role in the detoxification of As 5+ in C. vulgaris than PC. At concentrations below 100 mg/L cell surface binding and other mechanisms may play the primary role in As 5+ detoxification, whereas above this concentration As 5+ begins to accumulate inside the algal cells and activates a number of intracellular cell defence mechanisms, such as increased production of GSH. The overall findings complement field studies which suggest C.vulgaris as an increasingly promising low cost As phytoremediation method for developing countries.